Zytiga blocks production of testosterone, which can promote the growth of prostate cancer cells, but in a different way than established hormonal treatments.
This small, phase 2 trial involved 56 men with an average age of 58, all of whom had had at least three positive biopsies for prostate cancer.
For the first three months, 27 men received the standard hormonal therapy leuprolide alone, followed by leuprolide plus Zytiga for another three months.
The remaining 29 men received the two-drug combination for the whole six months, after which all men in both groups underwent prostate surgery.
One-third of the men who had received leuprolide plus Zytiga for the entire six months saw complete or nearly complete elimination of their cancer.
By comparison, only 15 percent of men in the other group experienced these results, the investigators found.
Those who received the combination for only 12 weeks had much lower response rates.
The participants also received low doses of the steroid prednisone to prevent side effects from Zytiga, although side effects overall were minimal, said Taplin.
It's not clear at this point why some men responded to the combination therapy while others did not, and that is an area that needs to be studied, the researchers said.
"In highly select people who have this aggressive type of prostate cancer, I think this is an important area to investigate," Brooks noted. "We need to figure out which patients would potentially benefit."
According to study author Taplin, the research received some funding from Johnson & Johnson, the maker of Zytiga. She said the drug is currently U.S. Food and Drug Administration-approved for patients with advanced prostate cancer that does not respond to hormone therapy, and costs about $5,000 per month.
The data and conclusions of research presented at medical meet
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